Cooling passages wafer blade assemblies for turbine engines, compressors and the like

ABSTRACT

A blade according to the present disclosure comprises a stack of a plurality of discrete wafers. A control passage of flow passages is provided on a planar surface of each wafer and means is provided for delivering coolant to the flow passages. The wafers are sufficiently thin as to permit thermal equalibrium between the wafers and the coolant flowing in the passages so that the blades are transpiration cooled.

United States Patent [191 Luscher et a1.

[ 1 Dec. 11, 1973 1 COOLING PASSAGES WAFER BLADE ASSEMBLIES FOR TURBINE ENGINES, COMPRESSORS AND THE LIKE [75] Inventors: Werner P. Luscher, El Dorado Hills; Leonard Schoenman, Citrus Heights,

both of Calif.

[73] Assignee: Aerojet-General Corporation, E1

- Monte, Calif.

[22] Filed: Apr. 22, 1968 211 Appl. No.: 723,203

[52] US. Cl 415/115, 416/90, 416/95, 416/229, 416/231 [51] Int. Cl. F0111 5/14 [58] Field of Search 253/3915, 39.15 B, 253/391 B, 77, 39; 415/115 [56] References Cited UNITED STATES PATENTS 3,301,526 1/1967 Chamberlain 415/115 3,163,397 12/1964 Gassmann 415/216 3,378,228 4/1968 Davies et a1. 416/95 2,853,271 9/1958 Findley 416/90 730,363 6/1903 Geisenhoner 416/191 Primary Examiner--Samuel Feinberg Attorney-Edward O. Ansell and D. Gordon Angus [57] ABSTRACT 2 Claims, 8 Drawing Figures PAIENIEUH M 1 I915 235178.183

sum 2 or 2 INVENTORS? WER/VEE P. LUSCl/Ek LE'OIVARO SCHOE/VMA/V COOLING .PASSAGES WAFER BLADE ASSEMBLIES FOR TURBINE ENGINES, COMPRESSORS AND THE LIKE This invention relates to blades and blade assemblies for use in turbine engines, compressors and the like.

In their most basic form, turbine engines include a combustion chamber, an air compressor located at the inlet of the combustion chamber for delivering compressed air to the combustion chamber, and a turbine driven by the hot combustion gases exhausted from the combustion chamber. In most conventional turbine engines, the turbine drives the compressor. Both the air compressor and the turbine include a plurality of radially disposed blades. One set of blades, often referred to as stator blades, is fixedly mounted to the turbine or compressor so as to direct gas toward the rotor blades. The rotor blades rotate about the axis along which the gas flows. In the case of a turbine, the stator blades direct the flowing combustion gases toward the rotor blades causing rotation of the rotor. The rotor of the turbine is usually connected by means of a shaft to the rotor of the compressor, thereby rotating the compres- Another object of the present invention is to provide blades constructed from a stack of wafers, the wafers having passages for coolant flow to cool the surfaces of l the blades.

Another object of the present invention is to provide blades constructed of interlocking stacks of wafers, the wafers having passages for coolant flow to cool the surfaces of the blades.

A blade according to the present invention comprises a stack of a plurality of wafers. A controlled pattern of flow passages is provided on a planar surface of each wafer and means is provided for delivering coolant to the flow passages.

According to an optional and desirable feature of the present invention, the flow passages include flow restrictor passages set back from the edge surface of the wafers so that coolant flow resistance through the flow restrictor passages is independent of local heat transfer conditions at the edge surface of the wafer.

According to another optional and desirable feature of the present invention, the wafers are arranged in interlocking stacks to form the blade.

According to another optional and desirable feature of the present invention, the wafers are sufficiently thin as to permit thermal equilibrium between the wafers and the coolant in the flow passages so as to cool the blades by transpiration cooling.

The present invention offers significant advantages over conventional cooling techniques in the following respects:

l. Precise flow control. Control of the flow of the coolant can be accurately maintained by varying the depth and/or length of the passage through the wafer,

and providinginternal manifold sizes conforming to the flow desired. Q i

2. Failure protection. The wafer type cooling design is not susceptible to failure caused by high pressure coolant erupting through a failure opening in the blade wall, since it is not necessary to maintain the coolant at a high pressure. Furthermore, localized overheating will not result in hot spot instability because the local coolant flow is uncoupled from the surface heat flux through the useof hydraulically isolated parallel coolant flow passages which have their hydraulic resistance significantlyremoved from the heated surface.

3. Cooling effectiveness. By permitting excellent thermal communication between the metal of the wall and the coolant at all points within the wall, the cooling capability of the coolant is completely exploited and the cooling efficiency is maximized.

4. Fabrication simplicity. Due to the basic simplicity and repetitious nature of the design, the same technology can be applied to blades of all sizes. Larger blades can be fabricated by using a number of smaller easily constructed modules.

The above and other features of this invention will be more fully understood from the following detailed description and the accompanying drawings, in which:

FIG. 1 is a top view elevation of a wafer for use in the blade illustrated in FIG. 4;

FIGS. 2A and 2B are top view elevations of other wafers used in the blade illustrated in FIG. 4;

FIG. 3 is a view taken at line 3-3 in FIG. 28;

FIG. 4 is a partly cutaway perspective view of a blade according to the presently preferred embodiment of the present invention utilizing a plurality of wafers illustrated in FIGS. 1, 2A and 2B;

' 'FIG. Sis a perspective view of a completed blade according to FIGS. 1-4;

FIG.6 is a top view elevation of another wafer for use in blades according to another form of the present invention; and l FIG. 7 is a'top view elevation of a modification of the wafer illustrated in FIG. 6.

FIG. 1 illustrates a wafer 10 for use in the presently preferred embodiment of a blade according to the present invention. Wafer 10 comprises manifolds l2 and 14 which provide fluid communication between a source coolant collant (not shown) and restrictor passages 16. If desired, a distribution channel 18 may interconnect manifolds l2 and 14. Each restrictor passage 16 pro vides fluid communication between a manifold and a flow passage 20 and serves to meter the flow of coolant to the flow passages. Flow restrictor passages 16 are preferably set back from the edge surface 11 of the wafers so that coolant flow resistance through passages 16 will be independent of local heat transfer conditions at the edge surface. Flow passages 20 provide fluid com munication between restrictor passages 16 and the edge surface of wafer 10. Preferably, flow diverters 22, in the form of small islands, are located in the flow passages. Flow divertcrs 22 are constructed so that their upper planar surfaces contact the lower planar surface of the adjacent wafer when the wafers are stacked together as illustrated in FIGS..4 and 5.

The wafers are preferably thin enough as to permit thermal equilibrium between the wafers and the coolant flowing in flow passages 20. This feature permits transpiration cooling of the blades formed bythe wafers to permit complete exploitation of the cooling capacities of the coolant. Furthermore, when the coolant is discharged onto the blade surface, it forms a film thereon, thereby film cooling the blade surface. By way of example, the thickness of each wafer is preferably between approximately 0.005 and 0.050 inch, and each restrictor passage 16 preferably provides an opening of approximately 0.00001 square inch. The space between flow diverters 22 forms holes on the edge surface of the wafer spaced approximately 0.015 inch apart.

The center portion of wafer is recessed on opposite sides forming channels 24 and 26 adapted to register with the wafers illustrated in FIGS. 2A and 2B.

FIGS. 2A and 2B illustrate wafers 28 and 30 which are adapted to interlock over channels 24 and 26 of wafers 10. Each wafer 28 and 30 preferably has a thickness of between 0.005 and 0.050 inch and contains distribution channels 32 adapted to be connected to a source of coolant (not shown). Channels 32 are in fluid communication through flow restrictor passages 34 to flow passages 36. Restrictor passages 34 meter the coolant flow to flow passages 36 and are set back from the passage terminating edge surface of the wafers so that the coolant flow resistance through the restrictor passages will be independent of local heat transfer conditions at the edge surface of the wafers. Each flow passage 36 has a flared design and contains a plurality of flow diverters 38 which forms a permeable edge surface of the wafers. Preferably, the flow restrictor passages are approximately 0.00001 square inch and the space between adjacent flow diverters is approximately 0.015 inch.

The individual wafers may be formed in any one of several different ways. One method known to those skilled in the art is the photoetching process. With the photoetching process, a thin sheet of metal is imprinted with an acid-resistant ink which outlines all the flow passages. The sheet is then immersed in an acid bath which etches out the flow passages at a precisely known, predetermined rate. Several depths of etch can be obtained on a single sheet of stock by repeating the above process with different passages. In this way, it is possible to form flow passages 36 and distribution channels 32 in wafers 28 and 30 and flow passages and distribution channels 18 in wafer 10 at different depths than restrictor passages 16 on wafers 10 and restrictor passages 34 on wafers 28 and 30.

It should be pointed out that it is possible to form the individual wafers by a variety of other methods, such as by embossing them or electroplating areas to form raised areas rather than etching out the depressed areas. Other means include but are not limited to, the utilizing of a crude etching process in the formation of all the passages with the exception of the restrictor passages which may be provided by a scribing process, similar to that used in preparing defraction gradings. The flow passages, distribution channels and restrictor passages may also be formed by conventional indentation processes or forming rolls. These methods are likewise well known to those skilled in the art.

The completed wafers 10 are stacked together forming stack 11 so that the planar surfaces of the wafers abut the planar surfaces of the next wafer. Wafers 28 and 30'are alternately stacked, forming stack 29, and the head portions 280 and 30a of wafers 28 and 30 provide coolant flow to the edge surface of each wafer while'the side portions contain wafers with alternate coolant flow passages.

For some applications it may be desirable to bond the wafers together. Bonding of the wafers can be accomplished in several different ways. One method is to electroplate to the thin sheet stock a thin flash of brazed material prior to applying acid resistant ink. The wafers so constructed will be provided with a coating of brazing alloy on all surfaces which contact adjoining wafers, but with none in any passageways through which coolant will be permitted to flow. The assembled wafers may then be placed in a furnace and brazed together.

Other methods which might be used for joining the wafers together are diffusion bonding, resistance welding, or simply applying some advanced bonding agent to the contacting surfaces.

When fully assembled, stack 29 of wafers 28 and 30 will provide a channel 40 which is adapted to fit over and register with the center body section between channels 24 and 26 of wafers 10. The assembled stack of wafers 28 is then assembled over the center body section of the assembled stack of wafers 11 as illustrated in FIG. 4 to form the fully constructed blade 41 illustrated in FIG. 5. The edge surfaces of the wafers forming stacks l 1 and 29 together form the fluid diverting surface of the blades.

FIG. 6 illustrates another embodiment of a wafer 42 for use in a blade according to the present invention. Wafer 42 comprises a hollow wafer having an insertable structural member 44 inserted within the chamber 46. Chamber 46 is connected to a suitable source of coolant (not shown) to provide coolant flow through metering restrictor passages 48 to flow passages 50. Flow passages 50 are preferably flared and restrictor passages 48 are set back from the passage terminating edge surface of the wafer so that coolant flow resistance through the restrictor through the restrictor passages will be independent of local heat transfer conditions at the edge surface. A plurality of flow diverters 52 in the form of islands, is located within each flow passage to divert flow of coolant to thepassage termi nating edge surface. Wafers 42 may be assembled together in a stack as hereinbefore described to form the completed blade. The edge surfaces of the wafers together form the fluid-diverting surface of the blade.

FIG. 7 illustrates a modification of the wafer integrally formed within each wafer. In the case of the wafer illustrated in FIG. 6, structural support member 54 is inserted into the passage 46 after the wafers have been completely assembled in a stack. The structural insert 54 abuts the walls of passage 46 of the wafers. However, in the case of the wafer illustrated in FIG. 7, structural members 54 are integrally formed within each wafer, thereby providing independent support for each wafer.

The blade constructed in accordance with the present invention may be used as a stator or as a rotor blade. The completed blade is mounted to a suitable supporting structure (not shown) such as a wall of the turbine or compressor in the case of a stator, or to a rotor assembly. In either case, manifolds 12 and 14 on wafers l0 and distribution channels 32 on wafers 28 and 30 are in fluid communication with a suitable source of coolant (not shown). A suitable pump (not shown) may be used to aid in delivering the coolant to the flow passages on the wafer. In the case of a rotor, a suitable manifold arrangement (not shown) may be provided in the wall of the rotor (not shown) which in turn is in communication with a supply of coolant (not shown) in the rotor shaft (not shown).

The attachment of the completed blade to the turbine or rotor may be accomplished by any suitable securing technique. By way of example, the blade may be bolted or bonded to the supporting structure.

The present invention thus provides improved blades and blade assemblies constructed of a stack of discrete wafers. The blade is effectively cooled by means of coolant flow through flow passages on a planar surface to the edge surfaces of the wafers. The blades are preferably thin enough as to permit thermal equilibrium between the coolant flowing in the flow passages and the walls of the wafers. Thus, the device permits transpiration cooling of the blades and allows complete exploitation of the coolant by using the coolant in transpiration cooling of the walls of the blade while it is flowing through the flow passages and by using the coolant to film cool the blade when it is subsequently discharged onto the blade surface. The efficiency and effectiveness of the coolant is therefore greater over prior cooling systems and consequently less coolant is necessary to cool the blades than was necessary in prior systems.

We claim:

1. A blade for a turbine, a compressor or the like, said blade comprising: a stack of a plurality of discrete wafers, said stack of a plurality of wafers comprising a first and a second stack of a plurality of wafers, the first and second stacks being interlocked to form said blade, each wafer having planar surfaces and edge surfaces, the planar surfaces of the wafers in the first stack being substantially perpendicular to the planar surfaces of the wafers in the second stack, the edge surfaces of the wafers together forming a fluid-diverting surface of the contact heat energy; a controlled pattern of flow passages on a planar surface of each wafer, said flow passages terminating at an edge surface thereof; and delivery means for delivering coolant to said flow passages; said wafers being sufficiently thin as to permit thermal equilibrium between said wafers and the coolant within the flow passages, whereby the blade is transpirationcooled by the coolant in the flow passages.

2. In a turbine engine having a stator and a rotor, said rotor being adapted to rotate about an axis; stator blades mounted to said stator; rotor blades mounted to said rotor; the improvement comprising at least some of said blades comprising a stack of a plurality of discrete wafers, said stack of a plurality of wafers comprising a first and a second stack of a plurality of wafers, the first and second stacks being interlocked to form said blade, each wafer having planar surfaces and edge surfaces, the planar surfaces of the wafers in the first stack being disposed substantially radially from said axis and the planar surfaces of the wafers in the second stack being disposed substantially tangentially to said axis; a controlled pattern of flow passages on a planar surface of each wafer, said flow passages terminating at an edge surface thereof; the passage-terminating edge surfaces of the wafers together forming a fluiddiverting surface of the blade, said fluid-diverting surface being adapted to contact heat energy; and delivery means for delivering coolant to said flow passages, said wafers being sufficiently thin as to permit thermal equilibrium between said wafers and the coolant within the flow passages, whereby the blade is transpirationcooled by the coolant in the flow passages. 

1. A blade for a turbine, a compressor or the like, said blade comprising: a stack of a plurality of discrete wafers, said stack of a plurality of wafers comprising a first and a second stack of a plurality of wafers, the first and second stacks being interlocked to form said blade, each wafer having planar surfaces and edge surfaces, the planar surfaces of the wafers in the first stack being substantially perpendicular to the planar surfaces of the wafers in the second stack, the edge surfaces of the wafers together forming a fluid-diverting surface of the blade, said fluid-diverting surface being adapted to contact heat energy; a controlled pattern of flow passages on a planar surface of each wafer, said flow passages terminating at an edge surface thereof; and delivery means for delivering coolant to said flow passages; said wafers being sufficiently thin as to permit thermal equilibrium between said wafers and the coolant within the flow passages, whereby the blade is transpiration-cooled by the coolant in the flow passages.
 2. In a turbine engine having a stator and a rotor, said rotor being adapted to rotate about an axis; stator blades mounted to said stator; rotor blades mounted to said rotor; the improvement comprising at least some of said blades comprising a stack of a plurality of discrete wafers, said stack of a plurality of wafers comprising a first and a second stack of a plurality of wafers, the first and second stacks being interlocked to form said blade, each wafer having planar surfaces and edge surfaces, the planar surfaces of the wafers in the first stack being disposed substantially radially from said axis and the planar surfaces of the wafers in the second stack being disposed substantially tangentially to said axis; a controlled pattern of flow passages on a planar surface of each wafer, said flow passages terminating at an edge surface thereof; the passage-terminating edge surfaces of the wafers together forming a fluid-diverting surface of the blade, said fluid-diverting surface being adapted to contact heat energy; and delivery means for delivering coolant to said flow passages, said wafers being sufficiently thin as to permit thermal equilibrium between said wafers and the coolant within the flow passages, whereby the blade is transpiration-cooled by the coolant in the flow passages. 